The present invention relates to a method for producing a construction, in particular a sandwich construction for the aeronautical and aerospace fields, and to a construction of this type, in particular a sandwich construction for the aeronautical and aerospace fields.
In high-tech fields, such as aircraft construction, sandwich constructions have a wide range of applications due to the good stiffness and strength to density ratios thereof. A sandwich construction is generally composed of a core layer which has a cover layer on the upper and lower sides respectively thereof.
In order to reinforce a sandwich construction of this type, it has become known to insert rod-shaped reinforcing elements, for example what are known as “pins”, into the core layer, a rigid foam for example, in the direction of the thickness thereof, before applying the cover layers on the upper and lower sides. Pins of this type may be produced in a pultrusion process for example. In pultrusion processes, initially dry fibres are impregnated with a thermosetting matrix and subsequently pulled through a heated extruder die. This causes the matrix to cross-link, at least in part, and this provides the reinforcing elements with a certain level of inherent rigidity to allow said elements to be introduced into the core layer.
The following approach has been developed in the state of the art to further reinforce the sandwich construction. The reinforcing elements are formed so as to be of such a length that they have a portion which projects beyond the upper and lower sides of the core layer. These projecting portions of the reinforcing elements are then folded over individually in a further step by a pair of heated tongs in such a way that they engage the core layer from behind. In a further step, the two cover layers mentioned above are applied on the upper and lower sides of the core layer, including the respective projecting portions of the reinforcing elements resting on said sides. The two cover layers, which are conventionally formed of a bonded fibre fabric which is pre-impregnated with a resin matrix, are subsequently cured together with the partly cross-linked reinforcing elements and the core layer under the effect of pressure and heat.
The approach described above has been found to have the drawback that it is necessary to initially grip each of the projecting portions of the reinforcing elements individually with the heated tongs and to then wait for a predetermined time until the projecting portion is sufficiently softened to enable it to be folded down so as to engage the core layer from behind. This process is comparatively time-consuming and therefore costly.
DE 10 2005 035 681 A1 discloses a manufacturing method for reinforcing core materials for sandwich constructions and for reinforcing sandwich constructions. DE 10 2005 024 408 A1 discloses a method for strengthening foam materials. U.S. Pat. No. 6,291,049 B1 discloses a sandwich construction and a method for the production thereof using pins.